[lammps-users] velocity on fixed part?

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1

Dear Lammps-users,

I fixed certain part of molecular model using: “fix 1 surface setforce 0.0 0.0 0.0”
And then I assigned initial velocity on the fixed part using: “velocity surface create 300.00 1265991662 mom yes rot yes dist gaussian” and run NVT simulation.

For this case, the initial velocity will be kept on the fixed part?
I checked that the initial velocity of the fixed part is not changed during simulation from the velocity dump file & also the position of the fixed part is not changed, too.
Since velocity is the rate of change of positions, I just wonder why the initial velocity is conserved during simulation even position is not changed.

I’d very much appreciate, if you give a comment on that.

Best,

S Lee

2

Did you run NVT on the atoms in the surface group? If so, they
should move. More standard would be to run NVE on those atoms.

If you ran NVT on other atoms, then the surface ones won't
move.

Steve

3

Dear Steve,

I checked my commands.
Yes, I only applied NVT on moblie atoms, not on fixed atoms.
Now it makes sense to me.

Thank you very much.

S Lee